- Etiology: Sepsis results in bacterial seeding of venous sinuses with the following organisms responsible:
— Neonates – Group B Streptococcus (most common), Escherichia coli, Enterobacter, Citrobacter
— Infants – Streptococcus pneumoniae (most common), Neiseria meningitidis, Haemophilus influenzae
— Children – Neisseria meningitidis - Imaging:
— MRI and CT may be normal in 50% or more
— Not generally indicated acutely for making the primary diagnosis but imaging does detect complications
— CT scan done prior to lumbar puncture to exclude increased intracranial pressure - Imaging CT:
— Findings can be subtle – meningeal and sulcal enhancement
— Increased density of cerebrospinal fluid
— Meningeal thickening - Imaging MRI Meningitis:
— Choroid plexitis and ventriculitis
— Arachnoiditis
— Vasculitis
— Cerebral edema
— Thick enhancing exudate in sulci and basal cisterns
— Secondary hydrocephalus
— Leptomeningeal enhancement
— Infarctions
— Brain edema
— Note: Meningeal enhancement may persist for months after treatment
— T1WI post contrast: Thickened enhancing meninges
— FLAIR: Lack of sulcal suppression and cerebrospinal fluid non suppressed (hyperintense cerebrospinal fluid on FLAIR)
— DWI: Lack of sulcal suppression and cerebrospinal fluid non suppressed (hyperintense cerebrospinal fluid on DWI) - Imaging MRI Brain Abscess:
— T2WI: Hypointensity
— T1WI post contrast: Thick and smooth enhancing ring due to hemorrhage and paramagnetic free radicals in macrophages
— DWI: Restricted diffusion due to pus - Imaging US Pyogenic Intraventricular Abscess:
— Echogenic ependyma
— Debris in ventricles
— Hydrocephalus - Imaging MRI Pyogenic Intraventricular Abssces:
— T1WI post contrast: Ependymal enhancement
— FLAIR: Incomplete suppression of intraventricular debris
— DWI: Positive - Note: Pyogenic intraventricular abscess is severe life threatening illness
- DDX: Viral meningitis – does not have diffuse leptomeningeal enhancement
- Complications:
— Acute: Venous sinus thrombosis, arterial occlusion and ischemia, extension to subdural space or brain abscess
— Chronic: Communicating hydrocephalus due to obstruction at arachnoid granulations, multicystic encephalomalacia, cortical and white matter atrophy, 10% of cases in first year of life develop arterial infarct - Treatment: Antibiotics
- Clinical:
— Most common CNS infection in children
— Diagnosis based on clinical (fever and meningeal signs and nausea and vomiting and seizures and vision changes) and cerebrospinal fluid criteria (lumbar puncture has increased white blood cells)
Subdural Effusion Post Meningitis
- Etiology: Seen with any organism (Haemophilus influenza, Streptococcus, Neisseria)
- Imaging MRI:
— Large often bilateral collections
— Isointense to hyperintense to cerebrospinal fluid
— Variable meningeal enhancement - DDX:
- Complications: Subdural effusion development during treatment of meningitis does not necessarily mean treatment failure
- Treatment: Resolves spontaneously
- Clinical:
— In less than 18 months of age (median age 5 months)
— In 20-40% of infantile meningitis cases
— No difference in outcome for meningitis with or without effusions
Radiology Cases of Bacterial Meningitis
Radiology Cases of Group B Streptococcus Bacterial Meningitis
Radiology Cases of Bacterial Meningitis With Intraventricular Abscess
